Insights on the paleoecology of Ammonia (Foraminifera, Rotalioidea) from Miocene carbonates of central and southern Apennines (Italy)

The Miocene transgression in central and southern Apennines is commonly represented by a sharp contact between shallow-water open-marine bioclastic limestones and the underlying Cretaceous or Eocene bedrock. Only in a few areas, very proximal marine or paralic deposits, witnessing the first stage of the transgression, have been preserved. These deposits contain rich foraminiferal assemblages commonly dominated by specimens of the genus Ammonia. The paleontological and paleoenvironmental analysis revealed that the Miocene Ammonia shared the same habitat and ecological requirements of living representatives from recent shoreline environments. Small Ammonia forma ‘tepida’ have been found in Miocene marginal paralic organic-rich bottoms with restricted water circulation and possibly under natural metal pollution. Big Ammonia forma ‘beccarii’ characterize Miocene nearshore marine bottoms with vegetated areas under fresh water inputs. The endoskeletal lamellar folding called tooth-plate, which characterizes recent representatives, is observed in fossil specimens of both tepida and beccarii morphogroups, testifying that there were no major changes in the shell architecture of Ammonia since the early Miocene.